In prior interactive TV systems, video data and any related enhanced content data are typically transmitted from a series of providers to a distribution station. From this distribution station, the data will be broadcast to a series of local transmitters from where it will be distributed to individual receivers, e.g. at houses. The video and enhanced content data can then be retrieved by users and displayed onto televisions.
The interactive TV system 10 of FIG. 1 comprises a series of providers 11a-c of video data and enhanced content data associated with (but carried by separate channels from) the video data. Each provider 11a-c transmits the enhanced content data to a distribution station 12. The distribution station 12 then broadcasts the data to a series of transmitters 13, only one of which is shown in FIG. 1. Transmitters are installed in each geographical area where the video data and enhanced content data are to be provided to viewers. These local transmitters 13 distribute the data to individual receivers 14a-c. The transmission of the data from the distribution station 12 to the transmitters 13 is done by a broadcast means: for example the distribution station could send the data over an uplink to a satellite, which could relay the data down to the transmitters 13. The transmission of the data from the transmitters 13 to the receivers 14 could be done by a local broadcast system, for example using radio or cable. To receive the data from the transmitters 13 the receivers may include aerials or satellite dishes, or units for receiving data transmitted by cable.
This system has the following disadvantage. If a popular television event such as a sports match is being broadcast at a particular time, then it can be expected that large amounts of data will be transmitted, in the form of enhanced content from data providers to receivers, and also from receivers back to an arrangement for receiving and analysing responses, in addition to the video data. Large amounts of bandwidth will be required for transmission during such a media-intensive event. This could be a particular problem when the data is distributed over a point-to-point channel such as the back channel (e.g. DOCSIS or modem) whose bandwidth is likely to be strictly limited, since in a point-to-point system the data must be transmitted separately to each receiver.
In relation to broadcast channels, normally a set amount of bandwidth is available for each channel. One possibility might be to reduce the bandwidth available to one channel so as to allow another channel to use an increased amount of bandwidth. However, if the data for the channels are provided by different sources it may not be possible to rely on one channel being able to use only a small amount of bandwidth at the time when the other channel requires an increased allocation.